Giant Villous Adenoma and the McKittrick-Wheelock Syndrome

Abstract

Introduction: McKittrick-Wheelock syndrome is a rare condition characterized by a rectal villous adenoma causing dehydration from diarrhea with severe hyponatremia, hypokalemia, metabolic acidosis, and acute renal failure. Case: A 63 year-old male with multiple admissions for hyponatremia was admitted with obtundation and dehydration. Labs showed Na+ = 100 mEq/L, K+ = 5.2 mEq/L, creatinine = 5.0 mg/dL, urine Na+ = 10 mmol/L. He was resuscitated with normal saline, but over 10 days, developed status epilepticus and abdominal distension. An abdominal CT depicted colonic distension and a rectosigmoid mass. (Fig A) Colonoscopy found 2.5L of thick mucoid fluid in the rectum, and underneath, a circumferential mass measuring 13cm long. Biopsies of the lesion revealed villous adenoma without dysplasia. (Fig. B) Analysis of the rectal fluid showed Na+ = 151 mEq/L, K+ = 11.7 mEq/L, and Cl− = 133 mEq/L, suggesting a secretory diarrhea. Indomethacin (25 mg PO TID) was given to decrease rectal effluent and help maintain electrolytes. Discussion: McKittrick-Wheelock syndrome is a rare cause of hyponatremia. The diarrhea is secretory with stool Na+ being isotonic to serum Na+ and stool K+ being 5–15x higher. The secretagogues cAMP and prostaglandin E2 (PGE2) alter intestinal electrolyte transport. Assays of secretory villous adenoma tissue have found 6x higher cAMP content and 17–38% higher cAMP protein dependent kinase activity. High levels of PGE2 have also been measured in villous adenoma related rectal effluent. Indomethacin is a way to block PGE2 production by inhibiting cyclooxygenase, therby decreasing rectal effluent and normalizing electrolyte imbalance prior to mass resection. McKittrick-Wheelock syndrome should be considered in the differential of recurrent severe hyponatremia. [figure 1][figure 2]Figure 1Figure 2